API-571 Exam - Topic 1 Question 116 Discussion

Actual exam question for API's API-571 exam

Question #: 116
Topic #: 1

A 5Cr-1Mo piping system in the hydrogen unit shows significant internal wall loss after 2 years in service due to CO corrosion. Which material would be best suited to use to install a new pipe system?

ATitanium

B9Cr-1Mo

CA-106 Gr B

D316 SS

Show Suggested Answer

Suggested Answer: D

by Roosevelt at Oct 17, 2025, 04:57 AM

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Laticia

29 days ago

I agree, 9Cr-1Mo seems like the best option overall.

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Olen

1 month ago

9Cr-1Mo has proven performance in similar conditions.

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Rodney

1 month ago

316 SS could work, but not ideal for CO corrosion.

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Eulah

1 month ago

A-106 Gr B might not hold up well in hydrogen.

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Ammie

2 months ago

Definitely not titanium; too expensive for this application.

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Lavera

2 months ago

Surprised 5Cr-1Mo failed so fast, thought it was more durable!

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Telma

2 months ago

A-106 Gr B? Really? That seems risky with CO corrosion.

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Boris

2 months ago

9Cr-1Mo is a solid choice for high temp and corrosion resistance.

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Wilbert

2 months ago

Hmm, I wonder if they have a "Vibranium" option. That would be the ultimate corrosion-resistant material, right? (Just kidding, of course.)

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Jeannetta

3 months ago

Titanium? Really? That's overkill and way too expensive for a piping system. Let's keep it practical, folks.

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Amber

3 months ago

316 SS is always a solid choice, but I'm not sure it's the most cost-effective solution for this particular application.

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Devorah

3 months ago

I think 9Cr-1Mo would be the best choice here. It's got good corrosion resistance and can handle the hydrogen environment.

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Bernardine

3 months ago

I think I'd go with 316 SS. It's a common material for corrosive services and should provide good resistance to the CO corrosion. The other options seem a bit more specialized.

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Desmond

3 months ago

Titanium is too expensive for this application.

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Olga

3 months ago

I think 9Cr-1Mo is a solid choice. Better corrosion resistance.

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Tamar

4 months ago

I think 316 SS would hold up better in hydrogen environments.

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Jesse

4 months ago

A-106 Gr B might be a cheaper option, but I'm not sure it would hold up as well in this kind of corrosive environment.

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Irma

4 months ago

I'm a bit confused on the differences between 9Cr-1Mo and A-106 Gr B. Can someone help me understand which one would be more suitable for this application?

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Dudley

4 months ago

Okay, I've got this. Titanium would be the best choice - it has excellent corrosion resistance, even in harsh environments like this. The other options just won't hold up as well.

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Trinidad

5 months ago

Hmm, I'm not too familiar with the specifics of these materials. I'll need to review my notes on corrosion resistance and hydrogen service to make an informed decision.

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Azalee

5 months ago

This seems like a tricky corrosion question. I'd need to think carefully about the properties of each material and how they might perform in a hydrogen environment with CO corrosion.

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Alexia

7 hours ago

But what about 316 SS? It’s known for its corrosion resistance.

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Janey

5 days ago

True, it has better resistance to CO corrosion.

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Paris

10 days ago

I think 9Cr-1Mo could be a good choice.

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Stephania

5 months ago

I think titanium is great for corrosion resistance, but it might be overkill and too expensive for this application. I lean towards 9Cr-1Mo based on what we practiced.

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Werner

5 months ago

I’m a bit uncertain about A-106 Gr B; I know it’s common for high-pressure systems, but I don’t recall its performance against CO corrosion specifically.

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Jaime

5 months ago

I feel like we did a similar question in class about material selection for corrosive environments. I think 9Cr-1Mo might be a better option because of its higher temperature strength.

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Tamra

6 months ago

I remember studying corrosion resistance, and I think 316 SS is good for acidic environments, but I'm not sure if it's the best choice for high temperatures.

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